WHEN the new generation of high-speed hand dryers began to arrive in public loos seven years ago, clean freaks rejoiced at these hi-tech machines that were said to dry hands in just ten bacteria-busting seconds.

But there's a downside, it seems, after a report last month revealed they're also unbearably noisy.

Researchers found their noise has the same impact on the human ear as a road drill. And some experts even claim hand dryers take longer to do their job than they claim. So what should you do? I asked the experts . . .

PAPER TOWELS VS HAND DRYERS Bacteria are more easily spread when your hands are wet, so if you're a shaker and don't dry your hands properly, you may as well not have bothered washing your hands.

Karen Clark, a microbiologist at Dyson, says: "Studies show that wet hands transfer 1,000 times more bacteria from one surface to another." The giants of the hand-drying world, dryer-makers Dyson and Kimberly-Clark, have been battling it out to convince us about their hygiene and planet-friendly credentials.

Kimberly-Clark published research showing jet air dryers increase bacteria on the hands. Although they could not explain why this would be the case, they believed it was because hands were left wetter, which meant they were more likely to pick up other bacteria in the environment.

According to their research, paper towels were the most effective way of drying hands.

Then Dyson commissioned a report, which found dryers were just as hygienic as paper towels.

Dr Ron Cutler, a microbiologist from Queen Mary's, University of London, says: "Our studies show hot dryers and paper towels are pretty much on a par. The cloth runner towels always come out worst - they do have issues with contamination."

Hugh Pennington, emeritus professor of bacteriology at the University of Aberdeen, agrees. "I don't think you can say one is better than the other - there's not much in it, except convenience."

DON'T RUB YOUR HANDS TOGETHER Many of us rub our hands together under a dryer to speed things up. But in the Dyson study by the University of Bradford, bacteria levels increased when people did this.

It's thought that bacteria in the skin can be brought to the surface when wet hands are rubbed together under a dryer.

Dr Anna Snelling, who ran the study, says: "The most hygienic method of drying hands is using paper towels, or a hand dryer that doesn't require you to rub your hands together."

It's also important not to touch the inside of the hand dryer, says Dr Cutler. "Some of the high-speed hand dryers have drainage holes - I sampled one and found that it was grossly contaminated."

Dyson's latest device is the Airblade, a tap fitted with air dryers so there's no need to walk from the sink.

COUNT TO 20

"In our studies, we have never found that any hand dryer reached the required limits of dryness in ten seconds," says Dr Cutler. "So far we've found 20 seconds is the most effective time, but no one is going to stand there for that long."

He says the best method may be to use a dryer first, then finish off with a paper towel - though the environmental impact would be significant.

NOISE FACTOR Last month, scientists at Goldsmiths, University of London, found noise from dryers was 'terrorising' vulnerable groups such as the elderly, people with dementia or conditions such as hyperacusis, which causes an over-sensitivity to sound, and children, particularly those with autism or Asperger's syndrome.

Dr John Levack Drever, head of the unit for sound practice research at Goldsmiths, who led the study, found high-speed dryers had significantly higher sound levels than those advertised, possibly because they were tested in laboratories and not in enclosed loos.

"I appreciate these are about hygiene and efficiency and ergonomics, but we are coming to a situation where people are stopping drying their hands," says Dr Drever.

He believes manufacturers should consider noise levels in future designs, and that installing noise-absorbent tiles in loos could help.

But he adds: "Some background noise in toilets is important because it creates privacy. And some managers like noisy dryers because they stop women congregating in the toilets and chatting."

Dyson said: "The Airblade conforms to EU Noise At Work regulations and poses no threat to hearing."

A modern, high speed hand dryer. Picture: ThinkstockSource: Supplied

IT'S WASHING THAT COUNTS "I don't think it matters how you dry your hands - the real problem we have is getting people to wash them properly," says microbiologist Professor Hugh Pennington.

In 2008, researchers installed soap dispensers in motorway service station loos across the UK. Of the 200,000 people who used the loos, only 32 per cent of men and 64 per cent of women used the dispenser. The advice is to put your hands under warm water, use soap and rub well, up to the wrists, in between the fingers and around the nails for 20 seconds - as long as it takes to sing the Happy Birthday song twice from beginning to end.

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